(a) Field of the Invention
The present invention relates to a magnetic toner composition, and more particularly to a magnetic toner composition having an improved chargeability and excellent uniform chargeability, and that is capable of reducing a difference in electrostatic charge between a toner remaining in a cartridge or in a developing unit and, that of a newly supplied toner.
(b) Description of the Related Art
The magnetic toner is used for developing latent images in electrophotography, electrostatic recording, electrostatic printing, etc.
In recent years, there has been high growth rate of printers and copiers with advanced technologies of PC and OA equipments. A method of forming a latent image has been widely used in many printers and copiers.
Generally, a fixed image is formed by the following processes:
1. An charge process of evenly offering an electrostatic charge to a photoconductive insulating layer made of a photo-conductive material;
2. An exposure process of forming latent image on the photoconductive member surface using light or laser beam;
3. A developing process of forming a toner image by developing the latent image using a developer;
4. A transfer process of transferring the obtained toner image to a transfer medium such as paper;
5. A fixing process of permanently fixing the transferred toner by heating or pressure application; and
6. A cleaning process of cleaning toners and adsorbents remaining on the photoconductive member.
The above-mentioned processes are repeated for successive image formation such as printed and copied sheets.
In the developing process above, a electrostatic charge is offered to the toner. For a two-component toner, the electrostatic charge is offered by mixing a carrier comprising ferrite with the toner. For mono-component toner, the electrostatic charge is offered by passing the toner through a narrow gap such as a sleeve and a doctor blade.
The toner to which the electrostatic charge is offered remains in a toner cartridge or in a developing unit, and a electrostatic charge is offered to the toner inside the cartridge or the developing unit by mixing with a agitating bar or agitating roller. A toner sensor inside the cartridge or in the developing unit detects existence of toners, and if the amount of remaining toners down small amounts, the toner sensor requests for supply of toner. If new toner is supplied, it is mixed with the toner remaining in the cartridge or in the developing unit. At this time, the newly supplied toner has no electrostatic charge while the remaining toner has been offered a electrostatic charge. The difference in electrostatic charge of the remaining toner and newly supplied toner causes blurred or nonuniform copying or printing images.
Accordingly, a magnetic toner composition having a uniform chargeability and excellent uniforn electrification, and that is therefore capable of reducing a electrostatic charge difference between the toner remaining in the cartridge or in the developing unit and a newly supplied toner, is highly required.